The present invention relates to polydiphenyldiacetylenes and particularly, to polydiphenyldiacetylenes obtained by a solid-state polymerization.
Such polydiphenyldiacetylenes according to the present invention are useful as functional materials such as non-linear optical materials, photosensitive materials, semiconductive polymer crystals and the like because they are obtained by solid-state polymerization of diphenyldiacetylenes.
In recent years, researches have been actively made on diacetylene compounds serving as monomers used for forming non-linear optical materials, photosensitive materials, semiconductive polymer crystals and the like.
For forming non-linear optical materials, photosensitive materials and semiconductive polymer crystals, polydiacetylenes obtained by a solid-state polymerization are used. It has been also already known that, in order to improve the non-linear optical effect of non-linear optical materials, the diacetylene monomers used must have an unsymmetrical structure and exhibit a large electronic effect owing to the conjugation bond between the main chain and the side chains.
It is generally known that some of diacetylene compounds represented by the following formula (I) have solid-state polymerizability. EQU R.sub.a --C.tbd.C--C.tbd.C--R.sub.b (I)
There is now a strong demand for monomers having solid-state polymerizability, an unsymmetrical structure and substituents which are conjugated with the diacetylene triple bonds. However, as each the above-described known diacetylene compounds having solid-state polymerizability has the same substituent at both ends of the diacetylene part, i.e., R.sub.a =R.sub.b in the formula (I), to form a symmetric molecule, a charge-transfer effect cannot be at all expected.
In addition, most of such diacetylene compounds have a structure in which the conjugation bond between the substituents and the diacetylene part is cut off. In this way, polymers in each of which the conjugation bond between the main chain and the side chains is cut off, exhibit substantially no electronic effect of the substituents R.sub.a and R.sub.b, and any substituents in the polymers have the tendency to exhibit similar properties.
On the other hand, since diacetylene compounds represented by the formula (I), having as the substituents R.sub.a and R.sub.b aromatic groups have conjugation bond between the triple bonds and the substituents, it is expected that the crystalline polymers formed have excellent electronic properties. However, most of such diacetylene compounds exhibit no solid-state polymerizability.
Some diphenyldiacetylene compounds each of which has two phenyl groups each having acetylamino groups at the ortho and meta positions or two phenyl groups each having trifluoromethyl groups at the 2- and 4-position, 2- and 5-position or 3- and 5-position, have solid-state polymerizability. However, each of these compounds has a symmetric structure in the molecule and thus exhibits no charge-transfer effect.
As described above, diacetylene monomers each of which has solid-state polymerizability, an unsymmetrical structure and aromatic groups as substituents which are conjugated with the diacetylene triple bonds, and each of which thus exhibits a large electronic effect, has been desired as the starting material of the non-linear optical materials.
European Patent 0 243 807 A discloses a process for production of a polydiacetylenic composition which comprises polymerizing a diacetylene monomer corresponding to the formula: ##STR2## (where X is an electron-donating substituent, Y is an electron-withdrawing substituent, and m is the integer one or two) and a polymeric composition which is characterized by the recurring monomeric unit: ##STR3## (where X is an electron-donating substituent; Y is an electron-withdrawing substituent; and n is an integer of at least 3). Further, as a concrete embodiment of the polymeric composition, European Patent 0 243 807 A discloses a preparation of polymer: ##STR4## obtained by casting a sample of 1-(4-N,N-dimethylaminophenyl-4-(4-nitrophenyl)-1,4-butadiyne in tetrahydrofuran on an optical glass substrate, evaporating the solvent to form a coating on the substrate, an heating the coated glass substrate at 250.degree. C. for ten minutes to produce a transparent continuous film of polymer on the glass surface. This polymerization is a liquid-state polymerization.
However, it is not said that the non-linear susceptibility of such polydiacetylenic composition is sufficient. Accordingly, it is strongly demanded to provide polydiphenyldiacetylenes having a high non-linear susceptibility, prepared by the solid-state polymerization of the corresponding diphenyldiacetylene monomers.
As a result of the inventors' studies for satisfying the above-mentioned demands, it has been found that by solid-state polymerizing diphenyldiacetylene derivatives represented by the following formula (II) having an unsymmetrical structure and exhibiting a large electronic effect. ##STR5## (wherein R.sup.1 denotes a hydrogen atom or a methoxy group; R.sup.2 denotes a hydrogen atom, a methoxy group or a methylamino group; R.sup.3 denotes a hydrogen atom or a trifluoromethyl group; and R.sup.4 denotes a hydrogen atom or a trifluoromethyl group; provided that R.sup.1 is not a hydrogen atom when R.sup.2 is a hydrogen atom, and R.sup.3 is not a hydrogen atom when R.sup.4 is a hydrogen atom), the obtained polydiphenyldiacetylenes are a single crystal polymer having a high non-linear susceptibility and a substantially 100% crystallinity in which the conjugated main chain is linearly oriented and which is the same size and shape as a crystal of the diphenyldiacetylene monomers and substantially free from faults.
The present invention has been achieved on the basis of this finding.